as you will notice, there are many different types of camera being used to film IV/AV videos. although i have no specific knowledge i would guess that these production companies are not using studio broadcast cameras. my guess would be a mix of pro camcorders and prosumer camcorders, depending on the shot/desired effect. even the recently released canon vixia series (hfs 21 for example) records 1920x1080 at 60i, 30p and 24p, bringing full high vision to the average person. i dont think they would be using any cameras over the $10,000 mark and they could be using cameras in the $4,000-$6,000 range and there would be little discernible difference to the untrained eye (like mine).
pro camcorders (and prosumer camcorders) are produced by all the main companies like sony, jvc, panasonic, canon and so on.